CARBONATE “CLUMPED” ISOTOPE DETERMINATION OF SEAWATER TEMPERATURE AND δ18O DURING THE END-TRIASSIC EXTINCTION EVENT

The end-Triassic mass extinction is one of the most severe biotic crises in the history of our planet. It has been hypothesized that the extinction was triggered by the rapid emplacement of the Central Atlantic Magmatic Province (CAMP), a large igneous province related to the initial rifting of the supercontinent Pangaea around 200 million years ago. As a result of CAMP volcanism, a massive amount of carbon dioxide (CO₂), sulfur dioxide, hydrogen sulfide, and other volatiles were released into the atmosphere, causing global climate changes and a mass extinction. A notable deposit of carbonate stromatolites known as the Cotham Marble (CM) is found in the uppermost Triassic strata of the Cotham Member of the Lilstock Formation in the Southwest United Kingdom. During deposition, the CM would have been located in the shallow Tethys sea between the paleocontinents of Laurasia and Gondwana. The CM stromatolites alternate between fine continuous lamination, and a dendritic structure that is infilled with other material. To quantify the magnitude of climate change across one of the largest extinction events in Earth history, we made clumped isotope measurements of both morphologies. We report preliminary estimates of water temperature and d18O derived from clumped isotope and oxygen isotope ratios. Initial data reveals plausible temperatures for seawater during the Late Triassic and a distinct difference between laminated and dendritic forms.